We have studied a total of 11 patients with subcutaneous injection of I-131 labeled Fab (antimelanoma, I-131, Fab 96.5 (.4 mCi and up to 10 mg and I-125 Fab 1.4 as a control dose, (.2 mCi and up to 10 mg). In 2 patients there was increased tracer localization in sites subsequently shown to have metastatic melamoma at the time of surgery. Surgical specimens have shown minimally specificity of targeting when comparing specific to non-specific. To determine if the non-specific binding in lymph nodes observed with In-111 9.2.27 could be related to the In-111 isotope release from the antibody 5 patients have been studied with I-131 9.2.27 and I-125 BL-3 as a control. While the high non-specific lymph node uptake was not seen in the scans counting of normal and malignant tissues showed non-specific concentration in normal nodes. At the time of subcutaneous injection patients complained of mild to moderate pain at the injection site which resolved quickly. The pain was more severe with the In-111 9.2.27 than with the other preparations. No allergic reactions were noted but 3 patients had local swelling erythema and itching that resolved within 72 hours. Future plans include evaluation of F(ab')2 fragments as well as their antimelanoma antibodies.